1. Field of the Invention
This invention relates to a band saw machine, more particularly to a band saw machine which permits quick and easy replacement of a band saw blade.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional band saw machine 1 is shown to include a machine frame 11 which has an upright frame body 111 and a sliding channel 112 formed in the frame body 111. A band saw blade unit 12 includes two first wheels 121 and a second wheel 122 spaced apart from each other, and a band saw blade 123 trained on the first and second wheels 121, 122. The first wheels 121 are rotatably disposed on the frame body 111 about their respective axes. A movable seat 13 extends and is disposed slidably in the sliding channel 112. The second wheel 122 is rotatably disposed on the movable seat 13 about its axis.
A releasing and replacing unit 14 includes a positioning shaft 141 which extends upwardly from the movable seat 13 and which is exposed from a top face of the frame body 111, and a compression spring 142. The positioning shaft 141 has a shaft body 143 which is connected to the movable seat 13 at one end thereof, and an abutting head 144 which is disposed on the other end of the shaft body 143 opposite to the movable seat 13. The compression spring 142 has two opposite ends abutting against the frame body 111 and the abutting head 144, respectively.
In use, the first and second wheels 121,122 rotate and move the band saw blade 123 for cutting an article. After a period of use, the band saw blade 123 will be worn out and become blunt, and thus often needs replacement. During replacement, the abutting head 144 is pressed downwards to cause the second wheel 122 to move toward the first wheel 121, so that the band saw blade 123 can be released, and the user can replace the band saw blade 123.
Although the aforesaid band saw machine permits replacement of the band saw blade 123, it still has the following drawbacks:
In order to prevent slippage of the band saw blade 123 during operation of the first and second wheels 121,122, the compression spring 142 has a very large biasing force. Hence, when replacing the band saw blade 123, a very great force is required to press the abutting head 144 downwards. Moreover, the abutting head 144 is relatively high, so that the user needs to raise his/her hand up high and press the abutting head 144 with a large force, which is inconvenient and laborious.